A Mayor Rahm Emanuel-backed move to bolster affordable housing rules in Pilsen and Little Village moved ahead Thursday, though an alderman who opposes the plan says the vote on the measure violated City Council rules.

The package hikes up the number of affordable units in the gentrifying neighborhoods to 20 percent of the total number in a development from 10 percent, and increases the per-unit cost developers must pay to get out of the requirements by $50,000.

Pilsen Ald. Daniel Solis, 25th, and Little Village Ald. Ricardo Munoz, 22nd — who are both retiring — back the plan. They say it’s an important step to preserving affordability for Hispanic families in historically Latino areas that are in danger of becoming playgrounds for wealthy white 20-somethings, especially when the city completes the Paseo mixed-use trail on an old railway right-of-way that’s envisioned as a Southwest Side version of The 606 train-track park, which has driven gentrification in Humboldt Park.

But Ald. Raymond Lopez, 15th, argues the ordinance is a half-measure that’s too late to preserve the makeup of Pilsen in particular. “Everyone in that room would readily acknowledge Pilsen is fully gentrified,” Lopez said. “If we want to protect parts of the city from gentrification, we should do so in parts of the West and Southwest sides where we want that development but haven’t seen it yet.”

Lopez called for a quorum in the Housing Committee, arguing the body was breaking council rules by taking a vote on the ordinance without a majority of the 15 members on hand. Committee Chairman Ald. Joe Moore, 49th, called a recess to try to drum up more members, and eventually passed the measure.

Lopez said it was illegal for Moore to take the recess action without a quorum, and the affordable housing measure therefore can’t head to the full City Council next week for an up-or-down vote. “I have reached out to the Inspector General’s Office to see how to proceed, because I don’t know that we have a clear precedent for this situation,” Lopez said.